National testing officials have apologized to 18 students at Center Moriches High School for the loss of their essay answers on the latest Advanced Placement U.S. history exam -- answers that required nearly nine months' study and two hours of writing.

Administrators at ETS of Princeton, N.J., the nonprofit agency also known as Educational Testing Service that administers tests, described...

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National testing officials have apologized to 18 students at Center Moriches High School for the loss of their essay answers on the latest Advanced Placement U.S. history exam -- answers that required nearly nine months' study and two hours of writing.

Administrators at ETS of Princeton, N.J., the nonprofit agency also known as Educational Testing Service that administers tests, described the loss this week as an "isolated incident."

The officials noted that they score more than 50 million answer sheets from AP exams and other tests each year.

Students have been offered the choice of retaking the essay portion of the test, canceling results and getting a refund of the $87 fee, or accepting "projected" scores based on their multiple-choice answers, which were not lost.

Russell Stewart, superintendent of Center Moriches schools, said he considered ETS' handling of the incident "very professional." But some students, now 12th-graders, protested that retakes would not be practical, because they will have full course schedules in the fall and will not have time to properly review for a test originally taken in May.

A classmate, Toney McFarlane, also 17, said he accepted ETS' offer of a "3" score, indicating that his performance on multiple-choice questions qualified as college-level work. Still, McFarlane feels deprived by the loss of his three essay answers, which normally would count as fully half his total score.

"I really worked hard on that, and thought that I'd done better than a '3,' " added McFarlane. "But now, I'll never know, because the paper's lost. I understand that accidents do happen, but they lost the whole package, and this test is for the future. You can't afford to make mistakes like this."

Advanced Placement is the nation's largest program providing college-level courses and exams in high schools. It is sponsored by the nonprofit College Board of Manhattan, with ETS handling logistics. Exams are scored on a range of 5 (extremely well qualified) to 1 (no recommendation), and most colleges grant credit for scores of at least 3 or 4.

How the test papers disappeared remains a bit of a mystery, according to local and national officials involved in the incident. Stewart, the superintendent, said that packages containing essay and multiple-choice answers from AP exams in various subjects, including U.S. history, were shipped from his district via UPS, and that all packages were assigned code numbers that allowed electronic tracking.

Becky Ford, an ETS spokeswoman, confirmed that the packages arrived at ETS. She added, however, that when packages were processed, handlers could not find the essay answer sheets, known as free-response sections, for U.S. history tests. Searches of warehouses failed to turn up the missing papers, another ETS official said.

"More than 99.9 percent of all testing materials are received and processed seamlessly, but we understand this is of little comfort to the affected students," Ford added in a prepared statement.

Debra J. Rice, director of test-taker advocacy for ETS, sent letters to the 18 students earlier this month, acknowledging that papers were missing, and adding, "I apologize for these unfortunate circumstances."Center Moriches's experience is not unique, though even ETS's critics acknowledge that such incidents are not common.

In 2006, the Washington Post and Edmonton Journal of Canada reported that sections from hundreds of AP exams taken around the world had been lost, including essays for 168 Canadian students. Tom Ewing, another ETS spokesman, was quoted as saying at the time that some score sheets go missing each year for a variety of reasons, including warehouse losses.

"It does not seem to be a huge problem, but it is a consistent enough problem from year-to-year that it is clearly an unsolved problem," said Bob Schaeffer, public education director for FairTest, a nonprofit advocacy group that is critical of standardized testing.

Superintendent Stewart calculated that ETS's offer of projected scores, if accepted by all 18 students, would result in scores averaging 3.4, compared with an average 3.0 registered by 22 local students in 2011, when essay results were included. "The College Board was very apologetic and, as far as the Center Moriches school district is concerned, they acted in a very professional way," the schools chief said.

Janine Barr, a local parent who works in a neighboring school district, said the outcome may actually have helped her son, Robert, 16, who obtained a projected "3" score.

"He may have bombed out on the essays," the mother said. "This may have worked out for us, so I'm not going to get riled by this."

Another mother, Kelly Platt, said that her daughter Danae, 17, might well have secured a "3" rather than a "2", if her essays had been graded. Platt also said that any retake of the test might not be scheduled until winter -- possibly too late to be included in college applications.

"All the kids are going to need those scores for their college applications and they're not going to be available," Platt added. "And that's unacceptable."